Mice with disrupted circadian rhythms exhibit symptoms similar to human depression, according to a study published in the journal Biological Psychiatry. Circadian rhythms are biological processes—such as sleeping and waking—that follow a 24-hour cycle. Most circadian rhythms are influenced by light. Disruptions in these rhythms can affect the body’s internal clock.
Can Disrupted Circadian Rhythms Cause Depression?
Previous research has found circadian rhythm disruptions may contribute to symptoms of depression. However, many of those studies have used manipulations that can independently affect mood. For example, some studies have altered light/dark exposure, but exposure to light can alter mood independently of its effects on circadian rhythms.
To circumvent this challenge, researchers injected mice with a drug that suppresses expression of a gene involved in driving circadian rhythms. This gene operates on the suprachiasmatic nucleus (SCN), a part of the brain that controls circadian rhythms. The injection reduced the expression of the gene by about 80%, significantly undermining the mice’s internal clocks. The mice were exposed to normal light/dark cycles to ensure changes in their behavior were not attributable to other circadian rhythm-altering factors.motivation and more hopelessness. Although they ate the same quantity of food as other mice, mice with suppressed circadian rhythms gained more weight.
Suppressing the gene appeared to alter mice’s response to stress. Mice with disrupted internal clocks showed abnormal corticosterone secretion patterns, particularly in response to stress. Corticosterone is a hormone linked to stress and immune reactions. Changes in corticosterone secretion point to increased anxiety and lowered immune function. Because the changes were especially pronounced in response to stress, the study suggests circadian rhythm interruptions can have even more of an effect during times of stress.
Understanding Environmental Depression Triggers
A variety of experiences can disrupt humans’ circadian rhythms. Stress, insomnia, and seasonal changes in exposure to light can affect the brain’s clock. Because the study involved mice, it does not conclusively prove circadian rhythm disruptions cause depression in humans. However, human and mouse brains are substantially similar, and both humans and mice are social creatures who draw important cues from their environments.
If future research finds a similar result in humans, circadian rhythms might play an important role in the understanding and treatment of depression.
Landgraf, D., Long, J. E., Proulx, C. D., Barandas, R., Malinow, R., & Welsh, D. K. (2016). Genetic disruption of circadian rhythms in the suprachiasmatic nucleus causes helplessness, behavioral despair, and anxiety-like behavior in mice. Biological Psychiatry, 80(11), 827-835. doi:10.1016/j.biopsych.2016.03.1050
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